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- #include <stdlib.h>
- #include <stdio.h>
- #include <stdint.h>
- #include <stdbool.h>
- #include <string.h>
- #include <elf.h>
- bool is_elf(const unsigned char* const buf, unsigned int bufsize, bool *is_64bit) {
- if (bufsize < EI_NIDENT) {
- return false;
- }
- bool valid = true;
- if (buf[0] != 0x7f) {
- valid = false;
- }
- if (buf[1] != 'E') {
- valid = false;
- }
- if (buf[2] != 'L') {
- valid= false;
- }
- if (buf[3] != 'F') {
- valid = false;
- }
- if (buf[EI_CLASS] == ELFCLASSNONE) {
- valid = false;
- }
- if (buf[EI_CLASS] == ELFCLASS64) {
- *is_64bit = true;
- } else {
- *is_64bit = false;
- }
- if (buf[EI_VERSION] == EV_NONE) {
- valid = false;
- }
- return valid;
- }
- void show_elf_header (Elf32_Ehdr* eh) {
- printf("e_ident = %s\n", eh -> e_ident);
- printf("e_machine = %x\n", eh -> e_machine);
- printf("e_version = %x\n", eh -> e_version);
- printf("e_entry = %x\n", eh -> e_entry);
- printf("e_phoff = %x\n", eh -> e_phoff);
- printf("e_shoff = %x\n", eh -> e_shoff);
- printf("e_flags = %x\n", eh -> e_flags);
- printf("e_phentsize = %x\n", eh -> e_phentsize);
- return;
- }
- void print_shdr(const Elf32_Shdr * const sh) {
- void print_type (uint32_t a) {
- switch (a) {
- case SHT_NULL:
- printf(" (SHT_NULL)\n");
- break;
- case SHT_PROGBITS:
- printf(" (SHT_PROGBITS)\n");
- break;
- case SHT_SYMTAB:
- printf(" (SHT_SYMTAB)\n");
- break;
- case SHT_STRTAB:
- printf(" (SHT_STRTAB)\n");
- break;
- case SHT_HASH:
- printf(" (SHT_HASH)\n");
- break;
- case SHT_DYNAMIC:
- printf(" (SHT_DYNAMIC)\n");
- break;
- case SHT_NOTE:
- printf(" (SHT_NOTE)\n");
- break;
- case SHT_NOBITS:
- printf(" (SHT_NOBITS)\n");
- break;
- case SHT_SHLIB:
- printf(" (SHT_SHLIB)\n");
- break;
- case SHT_DYNSYM:
- printf(" (SHT_DYNSYM)\n");
- break;
- case SHT_LOUSER:
- printf(" (SHT_NOTE)\n");
- break;
- case SHT_HIUSER:
- printf(" (SHT_NOTE)\n");
- break;
- default:
- if (SHT_LOPROC < a && a < SHT_HIPROC) {
- printf(" (reserved)\n");
- }
- break;
- }
- }
- if (sh == NULL) {
- printf("print_shdr: null ptr\n");
- return;
- }
- const char *names[] = {
- "sh_name", "sh_type", "sh_flags", "sh_addr", "sh_offset",
- "sh_size", "sh_link", "sh_info", "sh_addralign", "sh_entsize"
- };
- for (unsigned int i = 0; i < 10; ++i) {
-
- uint32_t *x = (uint32_t*)((char*)sh + (sizeof(uint32_t) * i));
- printf("%s = %x", names[i], *x);
- switch (i) {
- default:
- printf("\n");
- break;
- case 1:
- print_type(*x);
- break;
- }
- }
- }
- void print_phdr(const Elf32_Phdr* const ph) {
- if (ph == NULL) {
- return;
- }
- const char *names[] = {
- "p_type", "p_offset", "p_vaddr", "p_paddr",
- "p_filesz", "p_memsz", "p_flags", "p_align"
- };
- for (unsigned int i = 0; i < 8; i++) {
- uint32_t *x =(uint32_t*)((char*)ph + (sizeof(uint32_t) * i));
- printf("%s = %x\n", names[i], *x);
- }
- }
- void* init(char * const buf, const unsigned int bufsize, unsigned int offset) {
- if (buf+offset > buf+bufsize) {
- printf("invalid (%x, %x)\n", buf+offset, buf+bufsize);
- return NULL;
- }
- return (buf+offset);
- }
- int elf_get_number_of_sections(unsigned char* elf_file, unsigned int len) {
- bool is_64bit;
- if (!is_elf(elf_file, len, &is_64bit)) {
- return -1;
- }
- int no_of_sections;
- if (is_64bit) {
- Elf64_Ehdr *eh;
- eh = (Elf64_Ehdr*)elf_file;
- no_of_sections = eh -> e_shnum;
- } else {
- Elf32_Ehdr *eh;
- eh = (Elf32_Ehdr*)elf_file;
- no_of_sections = eh -> e_shnum;
- }
- return no_of_sections;
- }
- void *elf_get_section_header(unsigned char *elf_file, unsigned int len,
- unsigned int n) {
- bool is_64bit;
- if (!is_elf(elf_file, len, &is_64bit)) {
- return NULL;
- }
-
- int shnum;
- int shentsize;
- int shoff;
- if (is_64bit) {
- Elf64_Ehdr *eh;
- eh = (Elf64_Ehdr*)elf_file;
- shnum = eh -> e_shnum;
- shoff = eh -> e_shoff;
- shentsize = eh -> e_shentsize;
- } else {
- Elf32_Ehdr *eh;
- eh = (Elf32_Ehdr*)elf_file;
- shnum = eh -> e_shnum;
- shoff = eh -> e_shoff;
- shentsize = eh -> e_shentsize;
- }
- if (n > shnum) {
- return NULL;
- }
- unsigned int offset = n * shentsize + shoff;
- void *sh = init(elf_file, len, offset);
-
- return sh;
- }
- int elf_get_sh_flags(unsigned char *elf_file, unsigned int len,
- unsigned int n) {
- bool is_64bit;
- if (!is_elf(elf_file, len, &is_64bit)) {
- return -1;
- }
- void *section_header = elf_get_section_header(elf_file, len, n);
- if (section_header == NULL) {
- return -1;
- }
- int sh_flags;
- if (is_64bit) {
- Elf64_Shdr *sh = section_header;
- sh_flags = sh -> sh_flags;
- } else {
- Elf32_Shdr *sh = section_header;
- sh_flags = sh -> sh_flags;
- }
- return sh_flags;
- }
- int elf_copy_section_to_array(unsigned char *elf_file, unsigned int len,
- int n, uint8_t **array) {
- bool is_64bit;
- if (!is_elf(elf_file, len, &is_64bit)) {
- return -1;
- }
- void *section_header = elf_get_section_header(elf_file, len, n);
- if (section_header == NULL) {
- return -1;
- }
- unsigned int offset;
- unsigned int size;
- unsigned int type;
- if (is_64bit) {
- return -1;
- } else {
- Elf32_Shdr *sh = section_header;
- type = sh -> sh_type;
- offset = sh -> sh_offset;
- size = sh -> sh_size;
- }
- if (size <= 0) {
- return size;
- }
- unsigned char* source = elf_file + offset;
- if ((source + size) > (elf_file + len)) {
-
- return -1;
- }
- *array = (uint8_t*)malloc(sizeof(uint8_t) * (size));
- memcpy(*array, source, size);
- return size;
- }
- #ifdef STANDALONE
- char *loadfile(const char *fname, unsigned int *s) {
- FILE *f = fopen(fname, "rb");
- unsigned int size = 0;
- unsigned int rcnt = 0;
- if (f == NULL) {
- perror("file handler is null ptr");
- return NULL;
- }
-
- fseek(f, 0, SEEK_END);
- size = ftell(f);
- rewind(f);
- char *buf = (char*)malloc(sizeof(char) * size);
- if (buf == NULL) {
- perror("buf is null after malloc");
- free(buf);
- return NULL;
- }
- rcnt = fread(buf, sizeof(char), size, f);
- if (rcnt < size) {
- perror("read count < size");
- free(buf);
- return NULL;
- }
- fclose(f);
- *s = rcnt;
- return buf;
- }
- void test_00(Elf32_Ehdr * eh, char *buffer, unsigned int bufsize) {
- for (unsigned int i = 0; i < eh -> e_phnum; ++i) {
- printf("-- program header %.2i --\n", i);
- unsigned int offset = i * (eh -> e_phentsize) + eh -> e_phoff;
- Elf32_Phdr *p = init(buffer, bufsize, offset);
- print_phdr(p);
- printf("-----------------------\n");
- }
- for (unsigned int i = 0; i < eh -> e_shnum; ++i) {
- printf("-- section header %.2i --\n", i);
- Elf32_Shdr *sample;
- unsigned int offset = i * (eh -> e_shentsize) + eh -> e_shoff;
- sample = init(buffer, bufsize, offset);
- print_shdr(sample);
- printf("-----------------------\n");
- }
- }
- void test_01(unsigned char* elf_file, unsigned int len) {
-
- int count = elf_get_number_of_sections(elf_file, len);
- if (count <= 0) {
- printf("!\n");
- return;
- }
- for (unsigned int i = 0; i < count; i++) {
- int flags = elf_get_sh_flags(elf_file, len, i);
- printf("flag: %x\n", flags);
- }
- }
- int main(int argc, char ** argv) {
- if (argc < 2) {
- printf("usage: program filename\n");
- return 0;
- }
- unsigned int bufsize = 0;
- char *f = argv[1];
- char *buffer = loadfile(f, &bufsize);
- bool is_64;
- if (!is_elf(buffer, bufsize, &is_64)) {
- return 0;
- }
- Elf32_Ehdr *eh;
- eh = (Elf32_Ehdr*)buffer;
- show_elf_header(eh);
- test_00(eh, buffer, bufsize);
- test_01(buffer, bufsize);
- uint8_t *test = NULL;
- int c = elf_copy_section_to_array(buffer, bufsize, 1, &test);
-
- if (test != NULL) {
- for (unsigned int i=0; i < c; i++) {
- printf("%x, ", test[i]);
- }
- printf("\n");
- }
- free(test);
- free(buffer);
- return 0;
- }
- # endif
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